It is common to use earphones or headphones when a listener/user listens to/hears the sound from equipment such as a portable audio player, for example, a CD player or an MD player, or a personal digital assistance. In this case, a cable is generally used to connect the equipment to the earphones.
In this case, a control box for volume adjustment and player operation control (to select music, to turn on or off a player, etc.) is normally provided halfway along the cable, and a switch is provided at the control box. Furthermore, in a case of an earphone main body equipped with a wireless function, a switch is provided at the earphone main body.
In many cases, a listener uses earphones with the portable equipment while he/she is jogging or working on some other things. In these situations, if the position of the switch is limited to one point on the cable in a case of switch operation for the control over the player or the like, the listener has to look for the position to operate the switch. This is slow and the listener may feel the operation cumbersome.
To overcome these disadvantages, there are proposed techniques for allowing the cable itself to include a switch function. With these cables, the location of switch operation is not limited.
[Patent Literature 1] Japanese Patent Application Laid-Open No. 05-301589.
[Patent Literature 2] Japanese Patent No. 3447225.
In a case of a switch according to Japanese Patent Application Laid-Open No. 05-301589, two conductive members are vertically distanced from each other and arranged in an outer skin to face each other, and conductive rubber is provided between the two conductive members. The switch is configured so that, if external pressure is applied to the switch, the two conductive members contact each other and become conductive and the switch is turned on.
In a case of a switch according to U.S. Pat. No. 3,447,225, two conductive members covered with conductive rubber are arranged within an outer skin to be distanced from each other, and the two conductive members contact each other and become conductive if external pressure is applied to the switch.
These conventional techniques have the following problems. Since each of the switches includes the conductive rubber, the resistance of the switch using the conductive rubber decreases and the switch possibly operates in an unintended way when the switch is bent.
Furthermore, if the switch is not pressurized by the hand but is bent, the switch is often easily turned on and tends to malfunction.